The present invention relates to a method for producing toner and the toner produced therefrom. More specifically, the present invention relates to surface treating toner with silicate and the toner produced therefrom.
Toners which contain hydrophilic functional groups on the toner surface, such as the sodio-sulfonated polyester emulsion aggregation (xe2x80x9cEAxe2x80x9d) toners, have the disadvantage of having high humidity sensitivity. Although these toners have exhibited satisfactory charging in the low-humidity zone (xe2x89xa620% relative humidity (xe2x80x9cRHxe2x80x9d), also known as the C-zone) and excellent fusing properties with wide fusing latitude, the tribocharge levels in the high humidity zone (xe2x89xa680% RH, also known as the A-zone) are low consequently leading to large RH sensitivity ratios (20% RH to 80% RH). Previous attempts toward improving the RH ratio of polyester toners included forming a hydrophobic fluoropolymer shell by seed polymerization on the toner particle surface; however, the fusing characteristics were adversely affected due to increasing the crease minimum fusing temperature (xe2x80x9cMFTxe2x80x9d) value 5-10xc2x0 C. to the level of styrene-based EA toner MFT.
Another recent surface treatment approach used cationic tetra-alkylated phosphonium and ammonium salts to complex chemoselectively with the toner""s surface sulfonate groups thereby rendering the particle surface more hydrophobic and allowing a 2-fold reduction in the tribocharging RH sensitivity. Cationic tetra-alkylated phosphonium or ammonium salts, such as stearyltributyl-phosphonium bromide (xe2x80x9cSTBPxe2x80x9d), which complexes chemoselectively at the sites of surface-bound sulfonate groups was used to treat the toner surface at the end of the EA process.
A toner in accordance with one embodiment includes a resin, colorant, and a silicate component bound to the toner surface.
A method in accordance with another embodiment includes preparing a colloidal solution of a sulfonated polyester resin by heating water, adding a sulfonated polyester resin to the heated water, and cooling. A colorant is added to the colloidal solution, followed by heating the resulting mixture to a temperature equal to or higher than the resin glass transition temperature. An aqueous solution of either an alkaline earth metal (II) salt or a transition metal salt is added to the heated colloidal solution whereby the coalescence and ionic complexation of sulfonated polyester colloid, colorant, and metal cation occur until the particle size of the composite is about 3 to about 10 microns in volume-average diameter having a geometric distribution of from about 1.13 to about 1.23. An aqueous slurry of the toner particle composite is heated to a temperature of from about 25xc2x0 C. to about 60xc2x0 C. The toner particles are chemically treated in the heated aqueous slurry with an aqueous solution containing a water-soluble silicate component.
This invention in embodiments thereof describes a process for chemoselective, optionally, in situ, surface treatment of sulfonated polyester EA toners dispersed in aqueous slurry. The toner particles are rendered more hydrophobic in nature with a reduced RH sensitivity ratio for tribocharging while maintaining the excellent fusing characteristics of the parent untreated toner. The silicate reagent functions as a tribocharge enhancer and flow aid. The present toners are suitable for known electrophotographic imaging methods, printing processes, including color processes, digital methods, and lithography.
Water-soluble silicates that include the cationic complexes of tetraalkylammonium and/or tetraalkylphosphonium, such as tetraethylammonium silicate (xe2x80x9cTEASixe2x80x9d), tetramethylammonium silicate (xe2x80x9cTMASixe2x80x9d), tetrabutylammonium silicate (xe2x80x9cTBASixe2x80x9d) and tetrabutylphosphonium silicate (xe2x80x9cTBPSixe2x80x9d), selectively attach to the surface sulfonate groups on these toners by ion exchange. This chemical surface treatment selectively targets the anionic sulfonate moieties on the toner surface by causing cation exchange of the complexed sodium cation (or other metal cation) for the tetraalkylammonium (xe2x80x9cTAAxe2x80x9d) or tetraalkylphosphonium cation (xe2x80x9cTAPxe2x80x9d). The silicate portion of the molecule is also incorporated onto the toner""s surface providing good toner flow upon drying. The present invention in embodiments thereof provides enhanced triboelectric performance and reduced RH sensitivity of surface treated polyester EA toner particles, which is suitable for an in situ chemical surface treatment, using water-soluble silicates that include large organic cations such as tetraalkylammonium and/or tetraalkylphosphonium. The organic cations are optionally substituted with C1 to C20 alkyl substituents, for example, methyl, ethyl, propyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, iso-pentyl, neo-pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, lauryl, tridecyl, tetradecyl, myristyl, pentadecyl, hexadecyl, cetyl, heptadecyl, octadecyl, stearyl, nonadecyl, cicosyl groups, and the like; aryl groups, for example, phenyl, benzyl, 2-phenyethyl, naphthyl, anthracenyl, phenanthrenyl, and the like; and mixtures thereof. The present toner material is suitable for color and black-white systems, electrophotographic imaging and printing systems, xerographic copiers and printers, including digital copiers, and the like.
Chemoselective treatment of the toner""s surface-bound sulfonate groups can be accomplished with water-soluble silicates that include the cationic complexes of tetraalkylammonium and/or tetraalkylphosphonium, such as tetraethylammonium silicate, tetramethylammonium silicate, tetrabutylammonium silicate and tetrabutylphosphonium silicate. Tetramethylammonium silicate as shown in Formula 1 is available as an about 10% (as SiO2) aqueous solution (SaChem, Austin, Tex.) with a pH of from about 11 to about 13. Silica dissolves above about pH 10.7 to about 11.0 and can therefore be prepared with organic bases such as TMA, which have dissociation constants greater that about 10xe2x88x923. As well, these quaternary ammonium ions are most likely absorbed on the surface of the silica which is rendered hydrophobic when covered with this organic base. See, ller, Ralph K. 1979. The Chemistry of Silica: Solubility, Polymerization, Colloid and Surface Properties, and Biochemistry. John Wiley and Sons, Inc. (New York), p. 150, 427, the disclosure of which is incorporated herein by reference in its entirety.
The quaternary ammonium cation, e.g. tetramethylammonium (xe2x80x9cTMAxe2x80x9d), ion exchanges with the complexed sodium cation (or other metal cation) for the sulfonate moieties on the toner surface, thereby creating a hydrophobic toner surface. Criteria in choosing a candidate compound for polyester EA toner surface treatment include: 1) cost-effectiveness and commercially availability; 2) water solubility for in situ chemical surface treatment in aqueous media; 3) selective reactivity with the surface-bound sulfonate groups only; 4) efficacy in enhancing A-zone tribocharge level and/or reducing the C-zone tribocharge level and thereby reducing RH sensitivity ratio at least about 2-fold; and 5) chemical stability in the final surface-treated toner, without adversely affecting other toner properties such as fusing and color performance. It has been found that TMASi fits the criteria #1 through to #4; results are in progress for evaluation of toner fusing and color performance (i.e., #5). 
This method includes chemoselective surface treatment of surface-bound sulfonate groups on EA polyester toners using water-soluble silicates that include the cationic complexes of tetraalkylammonium and/or tetraalkylphosphonium. The intent of the surface treatment method is to alter the toner particle surface chemistry by masking the sulfonate moiety, which is hydrophilic in nature, with a hydrophobic additive. This in turn will not alter the toner""s overall morphology or effect it""s fusing characteristics. Instead the toner will demonstrate enhanced negative tribocharging levels in high humidity A-zone (about 80 to 85% RH) and/or lower tribocharging levels in low humidity C-zone (about 20% RH) and therefore reduce the RH sensitivity ratio for tribocharging (ratio of C-zone-to-A-zone charge levels). Reaction 1 depicts the chemical reaction scheme for the surface treatment, which is performed, for example, in situ at the end of the EA polyester toner-making process. 
EA polyester toners suitable for use in the present invention include those disclosed in and taught by U.S. Pat. No. 6,143,457 to Carlini et al., the disclosure of which is incorporated herein by reference in its entirety.
Furthermore, the toner includes a colorant such as cyan, black, magenta, yellow dispersion, or mixtures thereof with from about 20 to about 60 weight percent solids of resin and colorant; a toner wherein the colorant is carbon black; a toner wherein the colorant is a dye; a toner wherein the colorant is a pigment; a toner wherein the colorant is composed of a mixture of a pigment and a dye; and a toner which contains surface additives composed of metal salts, metal salts of fatty acids, colloidal silicas, metal oxides, or mixtures thereof which additives are each optionally present in an amount of from about 0.1 to about 2 weight percent.
Various known colorants, especially pigments, present in the toner in an effective amount of, for example, including from about 1 to about 65, from about 2 to about 35 percent by weight of the toner, or from about 1 to about 15 weight percent, and wherein the total of all toner components is about 100 percent, include carbon black like REGAL 330.RTM.; magnetites such as Mobay magnetites MO8029.TM., MO8060.TM.; and the like. As colored pigments, there can be selected known cyan, magenta, yellow, red, green, brown, blue, or mixtures thereof. Specific examples of colorants, especially pigments, include phthalocyanine HELIOGEN BLUE L6900.TM., D6840.TM., D7080.TM., D7020.TM., cyan 15:3, magenta Red 81:3, Yellow 17, the pigments of U.S. Pat. No. 5,556,727, the disclosure of which is incorporated herein by reference in its entirety, and the like.
Examples of specific magentas that may be selected include, for example, 2,9-dimethyl-subsituted quinacridone and anthraquinone dye identified in the Color Index as CI 60710, CI Dispersed Red 15, diazo dye identified in the Color Index as CI 26050, CI Solvent Red 19, and the like. Illustrative examples of specific cyans that may be selected include copper tetra(octadecyl sulfonamido) phthalocyanine, x-copper phthalocyanine pigment listed in the Color Index as CI 74160, CI Pigment Blue, and Anthrathrene Blue, identified in the Color Index as CI 69810, Special Blue X-2137, and the like; while illustrative specific examples of yellows that may be selected are diarylide yellow 3,3-dichlorobenzidene acetoacetamilides, a monoazo pigment identified in the Color Index as CI 12700, CI Solvent Yellow 16, a nitrophenyl amine sulfonamide identified in the Color Index as Foron Yellow SE/GLN, CI Dispersed Yellow 33 2,5-dimethoxy-4-sulfonanilide phenylazo-4xe2x80x2-chloro-2,5-dimethoxy acetoacetanilide, and Permanent Yellow FGL. Colored magnetites, such as mixtures of MAPICO BLACK.TM., and cyan components may also be selected as pigments with the present method. The colorants, such as pigments, selected can be flushed pigments as indicated herein.
More specifically, colorant examples include Pigment Blue 15:3 having a Color Index Constitution Number of 74160, magenta Pigment Red 81:3 having a Color Index Constitution Number of 45160:3, and Yellow 17 having a Color Index Constitution Number of 21105, and known dyes such as food dyes, yellow, blue, green, red, magenta dyes, and the like. Colorants include pigments, dyes, mixtures of pigments, mixtures of dyes, and mixtures of dyes and pigments, and the like.
Dry powder additives that can be added or blended onto the surface of the toner compositions optionally after washing or drying include, for example, metal salts, metal salts of fatty acids, colloidal silicas, metal oxides like titanium, tin and the like, mixtures thereof and the like, which additives are each usually present in an amount of from about 0.1 to about 2 weight percent, illustrative are U.S. Pat. Nos. 3,590,000; 3,720,617; 3,655,374 and 3,983,045, the disclosures of which are incorporated herein by reference in their entirety. Additives include zinc stearate and flow aids, such as fumed silicas like AEROSIL R9725.RTM. available from Degussa, or silicas available from Cabot Corporation or Degussa Chemicals, the coated silicas of application U.S. Ser. No. 09/132,623 pending and U.S. Pat. No. 6,004,714 and the like, each in amounts of from about 0.1 to about 2 percent, which can be added during the aggregation process or blended into the formed toner product.
Developer compositions can be prepared by mixing the toners with known carrier particles, including coated carriers, such as steel, ferrites, and the like, illustrative are U.S. Pat. Nos. 4,937,166 and 4,935,326, the disclosures of which are incorporated herein by reference in their entirety, for example from about 2 percent toner concentration to about 8 percent toner concentration.
Imaging methods are also compatible with the present toners, as illustrated by for example a number of the patents mentioned herein, and U.S. Pat. No. 4,265,990, the disclosure of which is incorporated herein by reference in its entirety.